1. Field of the Invention
The present invention relates to axial and centrifugal pumps which utilize inducers. The present invention provides an inducer capable of operating over a wider range of flow rates with less risk of cavitation and a higher efficiency than would otherwise be possible.
2. Description of the Prior Art
In general when a pump is required to operate over a wide range of flow capacities and has an optimum rate of fluid in flow which takes place at the design duty point, the parts of the pump may undergo extensive wear resulting from cavitation whenever the pump is operated in a part-load flow region. The effects of cavitation are more pronounced in larger pumps and the wear owing to cavitation also increases with increasing rotational speed. Attempts to reduce the wear which is attributal to cavitation include limiting the interval of operation in the part load region but this is not always practical. It has also been proposed to utilize more wear-resistant material for those parts which are likely to be exposed to the effects of cavitation or to use wear-resistant inserts. These techniques, however, are not wholly effective and complicate the design of the pump.
The use of an inducer to conjunction with, for example, a centrifugal pump, has been found to be the most effective way of permitting the pump to operate over a wider range of flow rates than would otherwise be possible. There still exists, however, a need for further improvements to permit large pumps to operate over even wider ranges of flow rates without cavitation damage. This is particularly true, for example, for pumps used in a nuclear reactor powered electric utility where the flow rate through the pump must be varied widely to conform to electrical demands and further where the pump must be designed to operate for up to 20 years.